1. Field of the Invention
This invention is concerned with the manufacture of cyclic olefinic compounds. It is particularly concerned with the reduction of organic compounds having at least one benzene ring to olefins of similar cyclic structures, largely mono-olefins, in a calcium-ethylenediamine system.
2. Description of the Prior Art
The Birch reduction process is a well known method that has been used for a number of years to reduce aromatic hydrocarbons to diolefinic hydrocarbons. In the Birch reduction process, aromatic hydrocarbons are reduced by means of metallic sodium or lithium in liquid ammonia, in the presence of an alcohol. Sodium is very reactive and requires a great deal of caution in use and handling. Likewise, liquid ammonia has a very low boiling point and is therefore difficult to handle. It is obviously desirable to provide a safer and easier reduction process.
A lithium-amine system for reducing simple aromatic hydrocarbons to cyclic alkenes has been reported by Benkeser et al, J. Am. Chem. Soc., 77, 3230, 1955.
The reduction of aromatic compounds with calcium, ammonia, and ether has been reported by Dumanskii et al, J. Russ. Phys. Chem. Soc., 48, 994, (1916), Kazanskii et al, J. Gen. Chem. USSR, 8, 642 (1938), and Campbell et al, J. Am. Chem. Soc., 67, 282 (1945). The procedures reported by these workers are cumbersome and usually give products that are quite impure and difficult to separate. As a result, calcium reductions have never gained widespread acceptance and have been used only sporadically through the years.
The production of monoolefins from aromatic hydrocarbons in a reducing system utilizing calcium metal in a mixture of methylamine and ethylenediamine has been described by Benkeser et al, Org. Chem., 44, 3737 (Oct. 12, 1979). The reduction process was carried out at 0.degree. C. using calcium metal in an amount only slightly in excess of the stoichiometric quantity necessary to effect the reduction. When ethylenediamine was used alone as solvent with 25% excess calcium to reduce isopropylbenzene, a very low conversion resulted and 64% of the unreacted isopropylbenzene was recovered.
Filed of even date herewith, is a patent application, serial number 643,649, by the same inventors disclosing the reduction of organic compounds having at least one benzene ring to polyolefins in a calcium-amine-alcohol system, the calcium metal being used in large excess or alternatively in conjunction with an inert abrasive particulate substance. Unlike the invention described in the present application, the reduction in the copending application is carried out in the presence of alcohol, and polyolefins are produced having at least two double bonds. As will be seen below, other methods and operating conditions are employed in the invention of the present application. Moreover, the reaction products of the present invention are largely mono-olefins, diolefins being produced only under limited conditions.